SOUNDING like an elephant running sprints, Matthew Heller, a double bassist with the New World Symphony, rumbled through a swift, disembodied passage from Mozart’s Symphony No. 35. Twenty-nine years old, a thin man with small rectangular glasses and red hair, he hunched over his hulking instrument and moved on to snippets of Beethoven’s Symphony No. 5, Stravinsky’s “Pulcinella” Suite and Brahms’s Symphony No. 1. A crisp voice behind a black cloth screen asked him to replay sections with different tempos, better accents, a more even volume.

“I don’t think even Karajan took it that slow,” the voice said, referring to the sometimes ponderous Austrian maestro Herbert von Karajan, who died in 1989. “Can I hear a traditional tempo?”

Mr. Heller was struggling to play perfectly, yet with musicality and personality. For four months he had been practicing these excerpts in excruciating detail, preparing for auditions to win an orchestra job and a future in music. On this day in mid-November inside a theater lobby, the ordeal was hardly made easier by the window washer squeegeeing the glass door or by Beethoven’s “Eroica” playing from a video screen outside.

As it happens, though, this was no ordinary audition. It was a mock audition, a bit of play-acting painstakingly constructed to recreate the pressure of the real thing. Real auditions are torturous rituals, the crucible that every classical musician must withstand: a 10-minute blur of excerpts with consequences that can last decades. The results of those 10 minutes determine not just the future of a player’s career but also the eventual composition and sound of orchestras, including many of the world’s greatest.

Orchestras themselves tend to view auditions as a necessary, sometimes tedious duty. But the New World Symphony, a unique cultural animal in the heart of hedonistic South Beach, has turned auditions and other career-development duties into the core of its mission.

In the increasingly professionalized world of modern orchestras, where merely playing beautifully no longer guarantees musical greatness, ticket sales or successful capital campaigns, New World has set itself a distinctive mission: to mold graduates of elite conservatories and university music programs into the ultimate orchestra players while also trying to field a world-class performing ensemble. (The latest results will be on display at Carnegie Hall on Feb. 27 and 28.) The model player is not just a technical whiz but also a musician who can converse with the public, meld into an ensemble, generate interesting programming ideas, schmooze with donors and teach.

At a time when classical music faces declining audiences and, some say, irrelevance, the sort of mission espoused by New World is seen as crucial.

“For orchestras to survive in the current socio-economic environment,” said Henry Fogel, president of the American Symphony Orchestra League, “they’re going to have to mean something to people in the community who might never come to a subscription concert.”

It all started with a cruise ship.

A Carnival Cruise ship, to be exact. In his youth Ted Arison, the company’s founder, had hoped to be a pianist. Eventually abandoning that dream, he went on to build a fortune selling vacation packages. But he never lost interest in classical music.

He and his wife, Lin Arison, founded the National Foundation for Advancement in the Arts, which gives grants to artistically accomplished high school seniors. Then in 1986, while on vacation in England, they heard an impressive performance by young musicians. With their own city, Miami, notably lacking a professional orchestra, they put two and two together and decided to start a professional youth orchestra.

A mutual acquaintance led them to the conductor Michael Tilson Thomas, a former protégé of Leonard Bernstein and now leader of the San Francisco Symphony. It turned out that Mr. Thomas had long been thinking about the need to nurture young orchestra musicians. When he and Mr. Arison met, he presented a list of the things such an orchestra would need — a building, faculty, administration — and Mr. Arison signed off on each one.

“I said, ‘To do all of that you’d have to be like the czar of Russia,’ ” Mr. Thomas recalled. “He just kind of winked and said, ‘I’m close.’ ”

Mr. Arison, who was one of the world’s richest men when he died in 1999, eventually contributed $62 million.

After the orchestra’s start in 1987, there were bumpy moments. Local professional musicians worried about the establishment of a major nonunion orchestra with the power to draw big-name conductors and soloists. In Year 5 New World’s first board chairman was indicted in the big securities and loan scandal; eventually he went to jail.

Now finishing its second decade, the orchestra has reached a turning point. This season it became a resident group at Miami’s lavish new Carnival Center for the Performing Arts. And it is planning a $135 million hall and headquarters, designed by Frank Gehry (who, back in the 1950s, baby-sat for Mr. Thomas).

The City of Miami Beach has leased it the land for $1 a year, though the orchestra still faces the long haul of raising the money. The building will rise next door to New World’s current home, once an abandoned pornographic-movie theater, on Lincoln Road, where the tattooed, shirtless and chic parade by and pop music pulses from every doorway.

The world has other top-flight training orchestras, but none offer this amount of training and professional simulation under a maestro of the stature of Mr. Thomas. And none have New World’s endowment of $72.5 million (with an annual budget of $8.5 million), which gives it extraordinary security to pursue its unorthodox mission.

Looked at in one way New World is like a job simulation machine. It has all the trappings of the big time: weekly pay, a subscription series, nearly 70 concerts a season, tours, recordings and sophisticated brochures.

At the same time New World is a postgraduate training ground similar to a medical residency. Some of the most famous figures in classical music — including Yo-Yo Ma, Pinchas Zukerman, the Emerson String Quartet, Emanuel Ax, Joshua Bell, Midori and John Adams — stream in to spend time with the fellows, as the members are called. Players from the world’s storied orchestras — the Chicago Symphony, the Vienna Philharmonic, the Philadelphia Orchestra — coach them in the nuances of orchestra playing, audition taking, coping with revolving-door conductors.

Other experts teach practical matters: managing personal finances, talking to donors, even handling a journalist. And the fellows are sent out to teach in local schools, act as mentors to young musicians, play in nursing homes.

Mr. Heller, a solid, conscientious musician with a shy quality and a slow, thoughtful way of speaking, is in some ways a typical New World fellow. He is native of Tacoma, Wash., and a graduate of the New England Conservatory in Boston, with a master’s degree in performance from Northwestern. He volunteers as organizer of the fellows’ mock auditions, and he blogs, discoursing soberly on double bass affairs, the nature of performance, the artists who pass through New World and other matters (hellafrisch.blogspot.com).

Having become increasingly frustrated with the music world and having looked toward medical school as an escape, he won a place in New World in 2004. It was a resurrection, he said, adding, “It felt like maybe I was destined to do this after all.”

Now in his third year, Mr. Heller has taken about 10 major auditions, finishing as runner-up with the Naples Philharmonic in Florida and reaching the semifinals at several major orchestras, including the Metropolitan Opera and the Minnesota Orchestra: not bad showings.

“Being here has taught me what the experience is all about,” he said backstage one day. “Being around people who are winning jobs is a very inspiring thing and a very motivating thing.”

Mr. Heller was one of about 1,000 musicians who applied to New World in 2004 for about 30 openings. He and his colleagues stay for three years, with a fourth possible in some cases.

Most are single and in their mid- to late-20s. A quarter come from abroad. They are all given weekly stipends of $425 (and $30 in recording fees), and they live rent-free in two former hotels acquired by the orchestra. An Art Deco mural showing a scene of beach abandon (with painted-over nipples) adorns the circular lobby of one. Past it lies a lounge area with a large television and a U of couches and easy chairs, fellows slung over them.

Outside there’s a pool. Fellows loaf around the patio, where the occasional keg party or pig roast takes place. Except for the sounds of practicing that fill the halls — snippets of Strauss’s “Don Juan” and Mozart’s Bassoon Concerto on a recent afternoon — it feels like college.

One day last fall Mr. Heller lugged his double bass onstage at the Lincoln Theater for rehearsal. Other musicians pulled up on bicycles, instrument cases slung over their backs. They wore flip-flops and shorts in the steamy morning air. Mr. Thomas, a slim, lithe man, his hair still wet and slicked back from a shower, appeared on the podium. He wore an open-neck blue dress shirt, his sleeves rolled up to the elbow.

The orchestra was set to rehearse “The Sorcerer’s Apprentice” by Paul Dukas, a brilliant showpiece forever to be associated with Mickey Mouse thanks to “Fantasia.” After lecturing a bit on Goethe, whose poem inspired the work, Mr. Thomas began the rehearsal.

Conducting without a baton, he often sang, illustrating passages in a flexible tenor and exaggerating syllables like “yaaa-daaa, yaaa-dohhh” to illustrate a slurpy passion, sounding something like Jackie Mason and drawing smiles from his charges. At times he had sections of the orchestra play a passage in slow motion, forcing attention on every note.

He asked the trumpets at one point to sound more “roosterish” and “cackly.” Like a sorcerer himself, he conjured composers of the past. “That’s leftover Berlioz, but we can still make it great,” he said of one passage. In a fast section he told the orchestra members to be like racecar drivers: “Don’t flinch at the turns.”

I sat onstage near a small, spiky-haired young woman in white cowboy boots and cutoff jeans who was harrumphing on a contrabassoon. The sound of the orchestra was explosive, and the musicians registered their approval of one another in the traditional way: by scraping their feet, sticking out a leg, shaking a foot.

Not yet jaded by the professional world, they were on the cusp of careers in an incredibly competitive world, struggling to establish the self-confidence of professionals. They chafed, sometimes, at the school-like aspects of New World but also fretted about the real world they would soon be thrust into. Their efforts to project optimism and idealism were touching.

“There’s very few things more exciting than being part of a huge machine, part of a huge effort,” said Naomi Gray, a cellist. “The power of music is monumental, and the more I play here, the more I realize that.”

But they would soon be heading into a particularly busy audition season. Over the next two months tryouts were being held for a number of positions, including principal percussionist at the Chicago Symphony, second trumpeter at the St. Louis Symphony, cellist at the Detroit Symphony, bassoonist at the Utah Symphony, violinist at the Philadelphia Orchestra and — of special interest to Mr. Heller — principal bassist at the Buffalo Philharmonic. New Worlders would all try for the openings, sometimes arriving in groups and often competing against one another.

From the outside, auditions seem like bizarrely mannered rituals, divorced from the context in which music is normally made. Candidates play a series of the hardest bits of one strand of an orchestral score. To eliminate favoritism, they are usually hidden by screens, their footsteps muffled by carpets lest the sound of high heels reveal their sex. Individual musicians play for an eye blink to prove they will be expert ensemble players — and good colleagues — for decades to come.

“It’s a stupid-human trick,” said Jeremy Branson, a percussion fellow. And it can be a crapshoot. The player who does not make it past the first round at the Podunk Symphony one year can win a job at the Chicago Symphony the next. But as many fellows acknowledged, no one has figured out a better way.

New World gives auditioners a powerful boost. It guarantees time off. It runs through so much repertory that players know the context of many passages they might be asked to perform. And because they rotate parts — from, say, first horn to fourth horn — they are prepared to audition for different roles.

Beyond that, New World emphasizes practical matters. What sound does the Chicago Symphony want from a cymbal? How do you react if a member of the audition committee yawns audibly? Should you ask to start over if you flub a passage? How do you deal with lousy hotels? Most important, how do you conquer fear, nerves and self-doubt?

The pivotal tool is the mock audition, which New World has refined into an art. Often the fellows contend with planned intrusions of ringing cellphones or rustling newspapers to steel them for the unexpected. Players audition for one another, for Mr. Thomas, for the outside coaches.

Always the point is the same: to see them safely married off to a new orchestra. “It hurts a little bit to say goodbye,” said Howard Herring, the orchestra’s affable president and chief executive officer. “But it is our job to move them on.”

It has done that job very well. Of the 676 alumni before this season started, New World said, at least 619 have jobs in music, most of them with professional orchestras. Sixteen alumni play in the so-called Big Five orchestras: Boston, Chicago, Cleveland, New York and Philadelphia. More than two dozen play in other elite orchestras, like those in Pittsburgh, St. Louis, San Francisco and Los Angeles. Others inhabit the ranks of regional orchestras or foreign groups like the Bamberg Symphony in Germany, the BBC Symphony in London and the Royal Stockholm Opera.

Despite that record of success, a current of anxiety runs through the fellows, particularly those in their third year. “It’s entirely possible I’m going to leave here and not have a job,” said Aaron Merritt, a cellist preparing for the Detroit audition, who called third year “death row.”

“You invest so much — not only money but practicing, anticipation and anxiety,” he added. “If you really want it, you have to be 120 percent prepared.”

For Elizabeth Jaffe, a 29-year-old violist from San Jose, Calif., the stakes were even higher. She decided that if she didn’t have a musical career by 30, she would move on, as inconceivable as that prospect was.

“I’ve been doing this forever,” she said. “I don’t know anything else.” While Mr. Heller was preparing for his big audition in Buffalo, Ms. Jaffe was trying for the job of assistant principal violist at the Richmond Symphony, even though she had never imagined herself as anything but a player in the middle of the section.

Until the fellows leave, Mr. Merritt said, preparing for auditions is “the No. 1 reason we are here.”

“We’ve been competing our entire life about getting into school, about winning a competition, about getting this seat in an orchestra,” he added. “It gets grating. I think we all notice it, an air of competitive energy.”

The other source of energy at New World is Mr. Thomas. During dinner at one of the more upscale spots on Lincoln Road, he spoke of New World as a place for the young players to take a sort of musical Hippocratic oath: “ ‘I will do this because of my love of learning and caring about people,’ as opposed to, ‘I can become such a star plastic surgeon that I can have a 19-car garage.’ ”

New World is also a “launching pad for people’s lives,” a sabbatical-like moment for young players to explore different ways to make a career in music, he said. “My personal mission is to have them hold onto ‘What does this mean?’ I’m trying to give the larger message of what music is all about.”

When in residence Mr. Thomas is a walking, talking master class. He meets with the fellows, collaborates with visiting luminaries, drops in on workshops, helps with mock auditions, holds training sessions.

To anyone who saw him as the boyish leader of the New York Philharmonic’s Young People’s Concerts in the 1970s, he is, at a strikingly energetic 62, an unlikely elder statesman. When I made a passing reference to Bernstein, he jumped into a discussion of Bernstein’s compositional technique, pointing out how a phrase from “On the Town” was borrowed from Mahler’s 10th Symphony after passing through an “Appalachian Spring” transformer. He sang each version of the theme with an emphasis on the common rising interval.

His view of classical music remains unabashedly messianic. “We’re living in a time in which every conceivable tradition is being exalted so much, every possible expression of art is sort of being considered to be the same,” he said. “What I’m saying is, ‘Listen, this is a 1,200-year-long tradition of classical music you’re talking about here.’ Basically from now back to the time of Gregorian chant it’s demonstrably a particular line of thought concerning what sound does, what music does.”

But he recognizes that those who carry on that tradition face pressures their forebears never knew. “Anybody who can play as a professional musician for 40 or 50 years and come out of it with his soul intact — or even better, well nourished — is the big winner,” he said.

In the days leading up to his big audition in Buffalo, Mr. Heller was touched by doubts about how much longer he could keep plugging away at the tryouts. “If I don’t get a job this year,” he told himself, “I could consider giving it another year. Then I would probably look for other options” — options outside music.

He took solace in something Jeffrey Turner, a bassist in the Pittsburgh Symphony, had said while coaching him at New World: “He said that if I don’t advance, it won’t be because I’m not a strong musical player. It will just be because of these little technical issues he’s been talking about with me. That was really important to me, because sometimes I have a hard time in having confidence. I don’t have a huge sound, or am naturally talented like I think other people are.”

Mr. Heller arrived in Buffalo a day early, hoping for an advance look at the hall. But he found that Neil Sedaka was playing there. Too uninspiring. He settled for looking at images on the orchestra’s Web site.

At the hotel breakfast the next day, he ran into an old friend: Scott Dixon, a New World alumnus. “We talked about New World stuff and people,” Mr. Heller said. Mr. Dixon was there for the same audition. Back in his room Mr. Heller could hear his friend practicing. “We got a little of the warm-up room syndrome already in the hotel,” he said.

His stomach in turmoil, he skipped lunch and went to the hall, where he was told he would be the 25th to play out of 65. His warm-up space was near the furnace and quite hot. But his hands were cold, so maybe the heat was good, he thought. “The whole thing is how you spin your own positive narrative out of it,” he said. He ate a banana, having heard somewhere that bananas contain tryptophan, which has a calming effect.

Only four excerpts were on the list. “Four excerpts,” he thought. “If I have to go home after four excerpts, that’s going to be a bummer.”

When his time came, Mr. Heller was told not to play a note until his first excerpt. (Many musicians have signature warm-up noodles, which can give their identities away.) Then he was directed to a long diagonal carpet that led to a pair of music stands. Earplugs from a previous concert littered the stage. He recognized lighting fixtures from the Web site.

The first item was the bass recitative in the “Ode to Joy” movement of Beethoven’s Ninth Symphony. Mr. Heller thought it was an auspicious opening: a big declarative statement that prefigures the bass vocalist’s solo line: “Oh friends, not these tones! Let us raise our voices in more pleasing and more joyful sounds!”

He said, “If you need to find your sound in a new place it’s a good one to do it.” His heart was pounding less than it usually did on such occasions. “I wasn’t feeling crazily nervous,” he said.

Then it was on to Beethoven’s Fifth Symphony, the famous bass passage in the trio of the scherzo. He tried to set a clear tempo and thought about Mr. Turner’s warning not to shortchange half-notes. But a diminuendo at the end could have been more graceful, with better vibrato on the last note.

The first phrase of a passage from Mozart’s Symphony No. 40 fell flat. He thought back to an audition panel the previous week, when the Toronto Symphony’s principal trumpeter, Andrew McCandless, stressed that showing the committee how you can recover from a mistake is just as valuable as playing perfectly. Don’t stop, he told himself.

Then came a passage from the last page of Strauss’s tone poem “Don Juan.” He had never seen it before, but he plowed through and nailed it. The audition was over. A laconic voice said, “Thank you.”

He joined others in the waiting room. An orchestra staff member came in with a little slip of paper. “She said, ‘Thank you very much for coming,’ ” Mr. Heller recalled. “ ‘The committee has actually chosen three of you.’ ” He was one of the three.

Mr. Heller had advanced to the semifinals. He walked out into the cold, empty streets of Buffalo feeling great. “I had something to celebrate,” he said. He called his mother to tell her.

The morning of his second round in Buffalo, Mr. Heller was checking out to move to a hotel closer to the hall when he ran into Mr. Dixon, the New World alumnus he knew from the auditioning circuit. He refrained from asking how Mr. Dixon had done the day before. “I didn’t want him to feel bad if he didn’t advance, and he probably thought I didn’t advance because I was moving my stuff out of the hotel. It was strange and awkward.”

He took the bus to the hall. While waiting for a warm-up room, he listened to a Chicago Symphony recording of “Don Juan” on his iPod, then in the same overheated room he played scales. The audition routine was the same, but this time there were six excerpts. “Again there was the ‘Thank you,’ ” Mr. Heller said. “It seemed like a little more encouraging ‘Thank you’ than the other day.” Back in the waiting room, after about 15 minutes, an official came in and announced that players Nos. 9 and 10 had advanced.

Mr. Heller was No. 12, and done with Buffalo.

“I’m trying to analyze every note I played and figure out, was that the one that revealed my ineptitude?” he said. “I’m realizing that was not the way to think about it. I just didn’t play stuff as well as you want to hear a principal player play it.” He wondered about his competitors. “I wasn’t good enough today, but who is? What’s the standard?”

Eventually the Buffalo Philharmonic picked a candidate for the principal job: Scott Dixon. Two months later, Mr. Dixon would win an audition for the more prestigious Cleveland Orchestra. And as for Elizabeth Jaffe, the violist who had given herself an ultimatum, the Richmond Symphony offered her the job of assistant principal. “I guess I kind of broke my curse,” she said, questioning her old back-of-the-section mind-set. “Maybe I am cut out for something.”

Other fellows won the jobs of principal oboist in San Diego and principal cellist in Memphis. In all, 10 New Worlders have found positions since the year began. “It certainly is a really fine start,” Mr. Herring said.

For those still looking, life went on at New World, with seminars on stage etiquette and how to reach new audiences; a concerto competition; a barbecue at the lavish home of the board chairman, Gerald Katcher, in Coconut Grove; and of course concerts.

Three weeks after Mr. Heller and Ms. Jaffe auditioned, they were back on the Lincoln Theater’s stage with the rest of the orchestra for a new-music concert, conducted by the Austrian composer H K Gruber.

First on the program were works by Brett Dean and James MacMillan, who introduced their pieces via an Internet2 hookup, their images broadcast on the wall behind the stage. Mr. MacMillan’s comments were recorded in Scotland, but Mr. Gruber interviewed Mr. Dean live from Australia. At intermission in the lobby, audience members came to shake Mr. Thomas’s hand.

Back in their seats, they heard “Frankenstein!!,” Mr. Gruber’s wild romp for orchestra, toy instruments and chansonnier. Mr. Gruber conducted while half-singing the score’s demented nursery rhymes and playing a slide whistle and other toy instruments. Ms. Jaffe and her fellow violists did double duty on kazoos.

Gavin Dougherty, the timpanist, blew up paper bags and popped them in time, balling them up and throwing them toward the audience. At one point the entire orchestra stood and sang. Players waved plastic hosepipes to create eerie whistling sounds. And when it was over, the audience gave a standing ovation.

After the concert many of the players gathered at Zeke’s, the cheapest watering hole along Lincoln Road, where beers are $3. “It felt really good to be back in front of all those people,” Mr. Heller said, “and with the section.”

"Only two things are infinite, the universe and human stupidity, and I'm not sure about the former."